Enhancement: Add URL input type

[saicheck2233]

Description: Add URL input type with validation. Below is the schema used for generating the URL input.

{
  "$schema": "http://json-schema.org/draft-03/schema#",
  "type": "object",
  "properties": {
    "s1": {
      "type": "string",
      "title": "An URL input",
      "format": "url",
      "description": "Example: www.domain.com"
    }
  }
}

Custom validation pattern is also supported if user does not want to use the default pattern validation.

Changes:

A generated form with URL type input.

Form would throws validation error if the value given is not a valid URL.

Validation passed if a valid URL is provided.